This invention relates to the reduction of AC voltage to a load. In particular, the system or method reduces AC utility power provided to a load.
AC utility voltage reduction is conventionally performed using large and heavy step-down AC transformers. Step-down AC transformers operate with about 96% efficiency.
Where miniaturization is desired, a variety of switchmode power supplies and conditioners have been developed, offering much smaller size and weight than conventional power transformers. However, switchmode power controllers operate at efficiencies of around 80-90 percent, much less than the standard transformer. Switch mode power controllers also operate at high frequencies (e.g. 50 kHz and higher) which generates copious amounts of electromagnetic interference (EMI). EMI is reduced by filtering and other techniques.
The use of switchmode power conditioners has been accelerated by government encouragement of the use of power factor controllers (PFCs). PFCs help maintain a high power factor, improving the utility's operating efficiency by reducing losses in power delivery. However, the utility's increase in operating efficiency through the use of switchmode PFCs is offset by the 10-20 percent efficiency loss penalty created by the PFCs.
U.S. Pat. Nos. 5,583,423 and 5,754,036 disclose energy saving power control systems and methods. The closed loop systems disclosed in these patents use the power measured at the load to control circuit functions, providing for efficient power reduction and power factor adjustment.